The present invention relates to the coupling of pipes which are malleable and deformable such as pipes made of stainless steel, copper and other metals.
Many types of pipe coupling systems are well known. However, when these systems are utilized to couple pipes made of materials of significant strength, such as stainless steel, the system or apparatuses utilized to couple two pipes together often fail with consequential failure to properly couple and seal two pipes together. Further, apparatuses associated with coupling the pipes together are often complex and there is a general need for a simple pipe coupling system, especially when utilized on stainless steel pipes or the like.
It is believed that proposals for crimped connectors for fluid type connections have not achieved significant acceptance due to lack of reliable and convenient characteristics which will meet quite specific requirements of regulatory authorities.
One example of a known crimped system is that of U.S. Pat. No. 4,257,155 (J J Hunter). This system relies on one pipe having a bell end and receiving in telescopic engagement the end of another pipe. A crimping tool is annularly engaged around the bell end portion to deform it inwardly and also to deform inwardly the underlying other pipe. Fluid tightness thus inherently depends upon such a metal to metal crimped joint and to be reliable may require complex flexible liners which may be difficult to engage and may be ineffective in use.
Another prior published system is that described in Australian patent application AU-A-13075/92 (Reid and Davies). This proposal has a rigid interior grooved connection member including a first deeper groove portion being adapted to contain an O-ring and a second adjacent portion being adapted to have crimped into it a portion of a telescopically engaged malleable pipe. The connection member having a relatively thick wall is received internally within the malleable pipe and significantly restricts the flow passage through the pipe.
By contrast to prior proposals the present invention proposes an arrangement which is believed to be practicable and effective at providing reliable fluid tight joints.
According to a first aspect of the present invention there is provided a method of connecting two malleable pipes comprising locating an end portion of one pipe inside the end portion of the other pipe with an O-ring located between the end portions, and using a crimping tool to apply inwardly directed crimping forces in a. radially inward direction around the O-ring and in a manner to cause radially inward deformation of both pipe portions immediately adjacent each side of the O-ring whereby the O-ring is deformed and partially flattened to establish a fluid tight seal between the pipes.
Most preferably, the deformable O-ring is one of two axially spaced O-rings and application of the crimping means involves a first crimping operation being applied across a first of the O-rings so as to form a crimp between the pipes on both sides of the first O-ring, and a second crimping operation being applied across a second of the 0rings so as to form a crimp between the pipes on both sides of the second O-ring.
The invention is generally applicable to pipes of malleable material; an especially important application of the invention is to stainless steel pipes which have many advantages in terms of inertness and capable of being worked. For example, the invention has been tested with stainless steel pipes having relatively small wall thicknesses, i.e. generally less than 1 mm and typically 0.7 mm and grade 304 or 316 stainless has been successfully trialed.
Although the crimping force can be applied uniformly around the periphery of the pipes, some discontinuity in the applied crimping force or the crimping means itself can be advantageous in some embodiments and in particular those where resistance to relative rotational motion of the two pipes about their axes is desired.
The crimping force is preferably provided by a crimping die which could be of the form for hand tool having two die carriers.
Another aspect of the invention consists in a kit or combination of parts comprising first and second pipes adapted for interconnection in accordance with the first aspect of the invention and flexible sealing means in the form of O-rings for cooperation therewith.
Another aspect of the invention consists in pipe joints made utilising any form of the invention as described above.